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Biomedical subjects

S B Pearson

Publications and source records attributed to S B Pearson.

At least 37 records · Page 2Linked to original sources
PubMed1991

The parasympathetic nervous system and the diurnal variation of lung mechanics in asthma.

In a placebo-controlled double-blind experiment the effects of cholinergic blockade with 30 micrograms kg-1 atropine administered by intravenous injection have been studied in nocturnal asthma. Cholinergic blockade at night reversed the changes in indices of airflow in small airways and of gas trapping to the values seen after administration of atropine during the daytime. However, the improvement in indices of airflow in large airways was not complete, reaching only the daytime placebo levels. No changes were seen in any aspect of breathing pattern. The results are discussed in relation to the literature.

Adult↗
PubMed1991

Time of development of tuberculosis in contacts.

The British Thoracic Association has recommended that close contacts of smear-positive cases of tuberculosis be followed up for at least 2 yrs (Tubercle 1978; 59: 245-259) but Selby et al. have recently suggested that a reduction in duration of follow up may be appropriate (Respir Med 1989; 83: 353-355). We have reviewed the results of contact procedures in Leeds to determine whether our experience supports reduction in the duration of follow up of contacts of patients with tuberculosis. In the 5-yr period 1983-87 there were 555 cases of tuberculosis (135 in Asians) of whom 42 (7.6%) were identified by contact procedures. In addition, contact procedures identified 35 children who were given chemoprophylaxis for positive Heaf tests (grade 2 or more). Of the 42 contacts with tuberculosis, 30 (71%) were diagnosed at the first visit, eight (19%) were diagnosed 6 months later and four (10%) were diagnosed 16-24 months after their initial clinic attendance. Five of the 42 contacts with TB were Asian, two of whom were diagnosed late. Seven out of ten non-Asian contacts who were diagnosed late had initial Heaf reactions of grade 1 or 2. All cases diagnosed late were contacts of a sputum-positive source. Poverty, as defined by residence in the Leeds Urban Priority Area, was associated with an increased risk of 3.3-fold for tuberculosis and a sixfold risk for chemoprophylaxis diagnosed by contact procedures.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Effects of H1-receptor blockade with terfenadine in nocturnal asthma.

1. In a single-blind placebo controlled study we have measured peak flow (PEFR) at 04.00 h and 16.00 h in eight asthmatics 6 h after placebo or terfenadine 120 mg, to determine if diurnal variation in histamine mediated effects contribute to nocturnal bronchoconstriction in asthma. 2. On placebo there was a significant diurnal variation in mean PEFR of 41 l min-1 (P less than 0.05). Terfenadine improved 04.00 h baseline mean PEFR from 242 to 278 l min-1 (P less than 0.05) but a 38 l min-1 diurnal variation in mean PEFR persisted (P less than 0.05). 3. We conclude that H1-receptor blockade with terfenadine may produce modest nocturnal bronchodilatation but does not influence the diurnal variation in PEFR in asthma suggesting that H1-receptor mediated effects are not important in the pathogenesis of nocturnal asthma.

Adult↗
PubMed1991

Regular nebulised terbutaline in chronic obstructive airways disease: dose-response studies fail to detect tolerance.

1. To determine the effects of high dose terbutaline on the possible development of tolerance we have examined the influence on dose-response of regular nebulised terbutaline. 2. We studied 10 subjects with severe chronic obstructive airways disease (COAD), mean age 63 years mean (s.e. mean) PEFR 142 l min-1 (19), FEV1 0.77 1 (0.12) and FVC 1.93 (0.19). Cumulative dose-response curves were measured (PEFR, FEV1 and FVC) to six incremental doses of terbutaline (0.5-8 mg) before and 1, 4, 8 and 12 weeks after starting nebulised terbutaline 5 mg four times a day. 3. Maximal bronchodilatation (Emax) was calculated by polynomial regression. Responses were examined by analysis of variance. 4. Mean baseline PEFR increased by 32 l min-1 (P less than 0.05), FEV1 by 0.16 1 (NS) and FVC by 0.54 l (P less than 0.05) after 12 weeks. Initial mean Emax PEFR was maintained throughout the study. The percentage of mean Emax PEFR achieved by each cumulative dose of terbutaline either increased (0.5 mg, 1 mg and 2 mg, P less than 0.01) or was maintained (4 mg, 6 mg and 8 mg) throughout the study. 5. We conclude that in severe COAD regular nebulised terbutaline 5 mg four times a day produces a sustained improvement in baseline lung function without changes in dose-response which would suggest tolerance.

Adult↗
PubMed1991

Dose response to inhaled salbutamol in chronic obstructive airways disease.

High dose inhaled salbutamol is increasingly used in the management of chronic obstructive airways disease. To determine the range of doses to achieve optimal bronchodilatation and the proportion of patients requiring high dose therapy we have studied 23 patients with chronic obstructive airways disease. Cumulative dose responses were measured to six incremental doses of salbutamol (0.2 to 1.2 mg) delivered by metered dose inhaler. Results were analysed by polynomial regression to calculate the smallest dose required to produce 90% maximal bronchodilatation in each patient. While 5/23 (22%) required greater than 1 mg the majority, 14/23 (61%), achieved 90% maximal bronchodilation with salbutamol 0.6 mg or less. The 8 patients with severe airflow limitation (FEV1 less than or equal to 1 litre) showed a similar pattern of response. We conclude that in chronic obstructive airways disease there are wide individual variations in the dose of inhaled salbutamol producing 90% maximal bronchodilatation with only a minority requiring high dose therapy.

Administration, Inhalation↗
PubMed1991

Platelet activation in nocturnal asthma.

Platelet activation may be a factor in the bronchial hyperresponsiveness that characterises asthma. As hyperresponsiveness is increased at night, changes in platelet activation over 24 hours were related to the diurnal changes in peak expiratory flow and plasma catecholamine concentrations in five subjects with asthma and five normal subjects. The effect of muscarinic receptor blockade with intravenous atropine at 0400 hours on these measurements was also studied. Platelet activation, assessed as the ration of beta thromboglobulin to platelet factor 4, was highest when the peak expiratory flow rate was at its lowest in the asthmatic subjects. There was no correlation between platelet activation and plasma catecholamine concentrations. Intravenous atropine did not alter the ratio of beta thromboglobulin to platelet factor 4, suggesting that parasympathetic activity is not the cause of the increased platelet activation at night.

Adult↗
PubMed1990

Adrenaline and nocturnal asthma.

OBJECTIVE: To determine whether the nocturnal fall in plasma adrenaline is a cause of nocturnal asthma. DESIGN: Double blind placebo controlled cross-over study. In the first experiment the nocturnal fall in plasma adrenaline at 4 am was corrected in 10 asthmatic subjects with an infusion of adrenaline after parasympathetic blockade with 30 micrograms/kg intravenous atropine. In the second experiment 11 asthmatic subjects showing similar variations in peak expiratory flow rate had the nocturnal fall in plasma adrenaline corrected by infusion before atropine was given. PATIENTS: Asthmatic subjects with a diurnal variation in home peak expiratory flow rate of greater than 20% for at least 75% of the time in the two weeks before the study. MAIN OUTCOME MEASURES: Peak expiratory flow rate and plasma adrenaline. RESULTS: Correction of the nocturnal fall in plasma adrenaline at 4 am to resting 4 pm levels did not alter peak expiratory flow rate either before or after parasympathetic blockade with atropine. CONCLUSION: A nighttime fall in plasma adrenaline is not a cause of nocturnal asthma.

Adult↗
PubMed1989

The effect of the circadian rhythm of vagal activity on bronchomotor tone in asthma.

1. The effect of the diurnal activity of the parasympathetic nervous system on bronchomotor tone and heart rate was studied in seven asthmatics with nocturnal asthma using both intravenous atropine and nebulised ipratropium at 04.00 h and 16.00 h. 2. A diurnal variation in vagal activity was demonstrated with higher vagal activity occurring at night. 3. There was a strong correlation between the initial response of both airway calibre and heart rate to vagal block both at 04.00 h and 16.00 h. However the duration of bronchodilation after vagal block was greater than with the heart rate suggesting differing sensitivities of pulmonary and cardiac muscarinic receptors to anticholinergic antagonists. 4. The bronchodilation seen after ipratropium was less than that after atropine suggesting that the intravenous route is preferable to study the physiological effect of vagal block in vivo.

Adolescent↗
PubMed1988

Parasympathetic nervous system in nocturnal asthma.

To investigate the effect of vagal blockade with atropine on nocturnal fall in peak expiratory flow rate 10 patients with asthma who had a diurnal variation in peak expiratory flow rate of greater than 20% were given 30 micrograms/kg of intravenous atropine or a placebo at 4 am and 4 pm. Vagal blockade caused significant bronchodilatation at 4 am and 4 pm (peak expiratory flow rate rose from 260 to 390 l/min at 4 am and 400 to 440 l/min at 4 pm) and significantly increased the pulse rate from 60 to 121 beats/minute at 4 am and from 76 to 122 beats/minute at 4 pm. Nocturnal asthma was almost totally reversed, implying that vagal mechanisms are fundamental in its pathophysiology. Other mechanisms--diurnal changes in plasma adrenaline concentration, the activity of non-adrenergic non-cholinergic nerves, and circadian rhythms of inflammatory mediator activity--may also be implicated.

Adult↗
PubMed1988

Inner city tuberculosis and immunisation policy.

Asian children, excluding recently arrived immigrants, had a similar incidence of tuberculosis to white children in Leeds from 1982-6. Children living in the urban priority area were 2.6 times more likely to develop tuberculosis than those living elsewhere. Selection for infant BCG immunisation should not depend on ethnic group alone.

Adolescent↗
PubMed1987

The effects of beta-adrenoceptor blockade on breathing during progressive exercise in normal man.

1 We have studied the effects of single oral doses of 80 mg propranolol and 100 mg atenolol on breathing during progressive exercise in nine healthy men in a double-blind, placebo-controlled experiment. As judged by their effects on exercise heart rate significant levels of beta-adrenoceptor blockade were achieved. 2 At the two lower levels of work rate (50 watts and 100 watts) minute ventilation on atenolol was lower than on placebo while at the highest level of work (200 watts) minute ventilation was higher on atenolol than on placebo. The regression of VE atenolol on VE placebo was 1.28 which is significantly different from unity (P less than 0.001). The results with propranolol were more scattered and failed to reach the 5% level of significance. 3 Effects on the pattern of breathing are small but when minute ventilation is matched with placebo, atenolol results in larger tidal volumes and prolonged inspiratory and expiratory time. 4 These observations are discussed in relation to other work in the literature.

Adrenergic beta-Antagonists↗
PubMed1985

The form and presentation of tuberculosis over a 10-year interval in Leeds.

Over the 10-year period 1973-82 1958 cases of tuberculosis were notified in Leeds (population 728 000). Records were traced for 1673 patients and analysed for age, race, sex, sputum status, site of tuberculosis, route of diagnosis and occupation. These results are presented. The tuberculosis screening service at the Leeds Chest Clinic diagnosed 172 cases of tuberculosis from 13 794 contacts screened and 41 cases from 12 572 newly arrived immigrants representing 10.3% and 2.4% respectively of the cases for whom records could be traced. Of these cases discovered by the tuberculosis screening service 25 were sputum positive. A further 15 cases were diagnosed from 2638 contacts screened by the static Mass Miniature Unit. The cost of the screening service at the Leeds Chest Clinic is estimated to be a minimum of 2000 pounds for every case of tuberculosis diagnosed.

Adolescent↗
PubMed1981

The effects of sustained lung inflation on the pattern of breathing in man.

1. Continuous positive-pressure breathing (CPPB) at airway pressures of 0.65-1.00 kPa above ambient pressure has been used to produce a sustained inflation of the lungs of approximately 1 litre in six normal male subjects. 2. Lung inflation produced a reduction in the ventilatory response to carbon dioxide inhalation by slow rebreathing in oxygen over approximately 45 min, with a reduction in the slope of the VE/Pet,CO2 and VT/Pet,CO2 relations (Pet,CO2, = end-tidal PCO2). 3. The pattern of breathing is altered, so that for any given expired minute ventilation (VE), tidal volume (VT) is reduced with a fall in breath duration (Tt) resulting from a decrease in inspiratory time (Ti) with no change in expiratory time (Te). 4. The break point on the VT/Ti relation is lowered.

Adult↗
PubMed1981

Neurological complications of Legionnaires' disease.

A case is reported of Legionnaires' pneumonia in a 49-year-old woman, associated with severe and permanent disability resulting from damage to the brain stem believed to be the result of an encephalitic process.

Apraxias↗